Dear Lifehacker,
My laptop battery doesn't last very long anymore. How can I tell what's going on or wrong with it and if it needs replacing?

Thanks,
Need a Battery Boost

Dear Need,
Laptop batteries do indeed get weaker and have limited lifespans (generally under three years but newer laptop batteries are coming out that last much longer). You don't say how old your laptop battery is, but here are a few resources and tips to give it a checkup.

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Testing and Monitoring Your Battery: Windows

Previously mentionedBattery Eater is a free Windows utility that can do a full load test on your battery and let you know how long it should last. If there's a discrepancy between what you're seeing from the program and actual experience, check out ways to extend your battery life (see below).

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Some Lifehacker readers have recommended instead BatteryBar, which comes in a free and pro version and lives in your system taskbar. It offers a visual display of your remaining battery life and keeps a history of your battery charge and discharge times so you can better gauge how long your battery will last.

Testing and Monitoring Your Battery: Mac

If you're using a Mac, we've described a tip before for using the built-in System Profiler (under Applications > Utilities) and go to "About this Mac" where you'll find information about the battery's health in the Power section.

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If you want to use a software program for monitoring your Mac laptop's battery health, we've recommended iStat Menuspreviously. The application provides detailed battery state info as well as advanced information for other OS X system properties.

What to Look For

If your laptop battery only holds about 50% try conditioning or recalibrating the battery (below). If it's 25% or less, consider buying a new one. Of course, also take age into account—a really old laptop battery will just need replacing.

Recalibrating Your Laptop Battery

Calibrating or recalibrating your laptop battery may recondition your battery to hold more charge again. We've described the process previously, which involves basically putting your laptop to sleep and fully charging it, then letting the battery fully drain again. Then charge your battery up to full again. Apple recommends doing this calibration when you first get your laptop and then every few months thereafter.

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Windows users can use a tool called BatteryCare, which not only monitors your discharge cycles but can also recommend when to calibrate your battery. For Mac users, Watts ($6.95) is a similar application with a reminder for when to calibrate, Growl notifications, and calibration assistance.

Maximizing Your Battery Life

That's all well and good, you're probably thinking, but after monitoring your battery life, if you're still having poor running times and your laptop battery looks healthy, there are some things you can do to maximize your battery life: switch to a power saver or balanced power plan, decrease the screen brightness, keep your laptop cool, and use hibernate mode. For more detailed descriptions of these suggestions and other tips, see our guide to extending your battery life. Good luck!